C# Linq 平均

Question

我有一个包含类似于下面的数据的表：

Group    TimePoint    Value
  1          0          1
  1          0          2
  1          0          3
  1          1          3
  1          1          5

我想投影一个表，如下所示：

Group    TimePoint   AverageValue
  1          0            2
  1          1            4

编辑：数据位于数据表中。

有人知道如何使用 LINQ 或其他方式来完成此操作吗？

谢谢。

Answer 1

您需要执行 Group By

您需要的 linq 类似于：

var query = from item in inputTable
            group item by new { Group = item.Group, TimePoint = item.TimePoint } into grouped
            select new
            {
                Group = grouped.Key.Group,
                TimePoint = grouped.Key.TimePoint,
                AverageValue = grouped.Average(x => x.Value)
            } ;

对于更多 Linq 示例，我强烈推荐 101 Linq 示例页面 - http://msdn.microsoft.com/en-us/vcsharp/aa336747#avgGrouped

Answer 2

这是一种更注重功能的方法（我更喜欢这种方法）。第一行无法编译，因此请用您的数据填充它。

var items = new[] { new { Group = 1, TimePoint = 0, Value = 1} ... };
var answer = items.GroupBy(x => new { TimePoint = x.TimePoint, Group = x.Group })
                  .Select(x => new { 
                                     Group = x.Key.Group,
                                     TimePoint = x.Key.TimePoint,
                                     AverageValue = x.Average(y => y.Value),
                                   }
                  );

Answer 3

你可以这样做：

IEnumerable<MyClass> table = ...

var query = from item in table
            group item by new { item.Group, item.TimePoint } into g
            select new
            {
                g.Key.Group,
                g.Key.TimePoint,
                AverageValue = g.Average(i => i.Value)
            };

Answer 4

假设有这样一个类：

public class Record
{
  public int Group {get;set;}
  public int TimePoint {get;set;}
  public int Value {get;set;}
}

var groupAverage = from r in records
                   group r by new { r.Group, r.TimePoint } into groups
                   select new
                          {
                            Group = groups.Key.Group,
                            TimePoint = groups.Key.TimePoint,
                            AverageValue = groups.Average(rec => rec.Value)
                          };